Lexie, 28, has known for most of her life that she would eventually need a new kidney. She has focal segmental glomerulosclerosis (FSGS), an autoimmune disease that causes the body to attack the kidneys.

She has been on dialysis for the past eight years. But over the past year in particular, she said she has felt her health deteriorating.

"I haven't been able to work very much lately," she said. "Most days, I feel like my body can't keep up with everyday living. I feel kind of trapped in this body that won't let me do things."

Lexie Libby needs a kidney. Her sister Emma was just cleared to donate one of hers. 2:00

Lexie's journey to get a kidney transplant hasn't been easy. She has faced numerous challenges, including multiple infections and a blood clot in her heart.

CBC News first spoke with Lexie and her family in 1994, when she was diagnosed. She lost her hair to chemotherapy treatments so her dad, Alger Libby, cut his hair in an act of solidarity with his daughter.

Many of her family and friends were tested to see if they would be a match for organ donation. None of them was.

Emma was tested when she turned 18, the required age to be an organ donor.

I wanted to make sure she could have that chance.- Emma Libby

"I remember being 16 or 17 and even wondering if I could apply then, because I just wanted to get it done as soon as possible," she said.

"I always felt like I was supposed to do it."

But Emma failed the blood pressure component of the test. When she found out she wouldn't be able to help her sister, she decided to quit smoking, get healthy and take the test again — in secret. She wanted to tell Lexie the news only if she passed that component.

"It made me really wake up and start taking better care of my body, because I wanted to be able to at least try again and get a little bit further this time," said Emma, now 21.

"I wanted to make sure she could have that chance."

Emma, Lexie and their older sister, Brittany Libby, when they were kids. (Supplied by Lexie Libby)

When Emma told her sister that she had retaken the test and passed, Lexie said the news renewed her strength to keep fighting.

"I'd been going through a really tough time at that point, because it was looking really hopeless for me," she said.

Now the sisters hope their story will give others hope and raise awareness about organ donation.

'Quite miraculous'

Dr. Lyle McGonigle, the pediatrician who first diagnosed Lexie, hopes so too.

"There is a huge need for transplants across Canada," he said. "The organ availability is just not there. There's a lot of people sitting on the transplant waiting list who aren't living the life they could if they got transplanted."

McGonigle has been with Lexie through all of the ups and downs of her disease.

He said it's "quite miraculous" what Emma did.

"It just warms my heart," he said. "I think Lexie is courageous, strong, deserving, and if she can live a better, more functional life, then that's really why we do what we do."

Dr. Lyle McGonigle has been with Lexie since he first diagnosed her disease when she was four years old. (Supplied by Lexie Libby)

McGonigle noted there's a chance the disease could reoccur in the new organ because FSGS is aggressive.

Regardless, Lexie said what her sister is doing will make her life better.

"Either way, whether the disease recurs or not, she's still giving me a second chance. And it's impossible for me to describe what that means. She really is giving me my life back."